Method and apparatus to enable swimmers to converse under water



Jan. 29, 1963 w. N. WAINWRIGHT ErAL 3,075,174

NETRDD AND APPARATUS To ENABLE swIMMERs To coNvERsE UNDER WATER Filed July 14, 1959 3,76,l7 Patented Jan. 29, 1.961

3,076,174 METHOD AND APPARATUS T ENABLE SWIM- MERS TO CONVERSE UNDER WATER Walter N. Wainwright, Waterford, Conn., and Russell I.

Mason, Barneveld, N.Y., assignors to the United States of America as represented by the Secretary of the Navy Filed July 14, 1959, Ser. No. 827,128 Claims. (Cl. 340-5) (Granted under Title 35, U.S. Code (1952), sec. 266) The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Thisinveution relates to underwater voice communication and more particularly to a method and apparatus to enable two or more divers or underwater swimmers to confer readily with one another or with personnel aboard a nearby vessel.

. A team of divers or underwater swimmers, referred to as swimmers hereinafter, working together under water are severely handicapped if they are not able to confer in the same manner as a team of men working together in air. Swimmers can function more safely and more efticiently if they are enabled to converse as readily as they can in air or over an even greater range than they can 1n air.`

An object of this invention is to provide a method and apparatus for swimmers to enable them to continuously confer while submerged, just aswellas they might confer Vin air, without manipulating any controls, over a distance ranging from bodily contact to several hundred feet apart, not requiring bulky or weighty encumbrances, and without electrical lead connections therebetween so as not to interfere with their freedom of movement under water.

A further object is to provide a compact, light-weight apparatus for a swimmer, for raising his sensitivity to waterborne. voice sounds far above that traceable to waterborne sounds detectable by his bone structure and transferable, thereby to his auditory nerve. Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawing wherein:

FIG. 1` shows a swimmer equipped in accordance with this invention, and

FIG. 2 is a block diagram of an embodiment of this invention excluding the mask into which the swimmer speaks. l

There are three factors that limit underwater voice communication. One factor is the impedance mismatch between the voice mechanism and the water plus the fact that increased ambient pressures adversely affect the voice; however, the effects of changes in ambient pressures on the voice are small in comparison to the eiects produced by impedance mismatch. If a mask is provided around the swimmers mouth to enable him to form words and speak, the intensity of the voice energy that enters the water is greatly reduced as a result of the impedance mismatch. Since pc of air is 42 and the pc of salt water is 154,000, an increase in pressure of approximately 60 times is required for the human voice to produce the same amount of power in water as in air. Power developed under water by shouting loudly into a mask supported around the mouth is approximately equal to that produced in air by reading audibly but at a soft vocal level. For the most part, vocal energy that is delivered by a swimmer to the water is liberated by surface portions of his body, such as his head, neck, chest, and back which are more closely matched to the water than his voice mechanism in the mouth. y This is particularly evidei when the swimmer shouts into his mask.

Noise generated by breathing apparatus is a secon factor that limits underwater voice communication. A open circuit self contained breathing apparatus generali utilizes compressed air which is contained in high pre sure cylinders worn by the swimmer. Breathing is accon plished by inhaling compressed air through a deman regulator and exhaling directly into the water theret generating a great deal of noise. A closed circuit sel contained breathing apparatus generates substantially le: noise than an open circuit apparatus. .It utilizes oxyge instead of compressed air and breathing is accomplishe by inhaling the gas that includes a predetermined pe. centage of oxygen and exhaling the exhaust through canister that absorbs carbon dioxide. The purified ga with the addition of oxygen as needed, is recirculated. N exhaust gas is liberated into the water. Far less noise generated by closed circuit breathing apparatus, but noni theless this noise level may interfere with voice commun cation. y

A third factor that limits underwater voice commun cation is that human hearing under water by way of tl natural hearing mechanism is negligible compared to th: in air. For a given sound pressure at a given frequenc under water, the amplitude of particle movement is a tin fraction of particle movement in the air for the sam sound pressure or frequency. The structure of huma ears are such that they are properly coupled, mechan cally, to air. Since the basic mechanism of hearing di pends on the amplitude of movement of the ear drun and since particle movement in water for sound pressure and frequencies corresponding to human conversation negligible compared to the particle movement in air,

r human beingthat relies on his natural hearing mechanisr under water is to all intents and purposes effectively dea: There is substantial evidence lto indicate that most of th energy of underwater sound is transmitted to the hearin mechanism, notby way of the ear drum, but by conduc tion through the bones of the body, particularly the skul as in the case of persons who are deaf as a consequenc of ear drum defects. Under water, a swimmer wit healthy ear drums and auditory nerve is nearly as dea as the swimmer Ithat lacks ear drums, but has health auditory nerves.

A method in accordance with this invention for er abling a team of swimmers to continuously confer uncle water despite the above described diiiiculties require that each swimmer be provided with a mask for deiinin an air space at least around his mouth and also require that his breathing apparatus be not of the type wherei the swimmer must grip an air inlet part with his teetl Self contained breathing apparatus including a breathin mask with a demand regulator is marketed commercially In U.S. Patent 2,456,130, there is shown a breathing mas including securing straps, viewing window, and valv means for passing gases of inhalation and exhalatio; suitable for use in carrying out the principles of this in vention. The mask is essential because with it the swim mer is able to open his mouth into an air space to form words and to speak and shout. Also, the swimmer i provided with a breathing air supply that may feed intl his mask or into his nose. The method also requires tha substantially all .of the surface area of the swimmer head, mask, chest, and back, be exposed tothe water, o where the swimmer must wear a cold weather suit th method requires the next best thing, namely, that th above-mentioned surface area of the swimmers bod; not be covered with pressure release or sound isoiatin material. At each swimmer, the method includes th steps of continuously intercepting and extracting frorI the water a traction of any vibrationalenergy in thi :er in the voice frequency range, amplifying the ex- :ted energy, continuously transferring the amplified ce frequency vibrational energy to the auditory nerve the swimmer, continuously providing an air space und the swimmers mouth into which he may speak `currently while listening to voice frequency energy, l continuously providing a breathing air supply to the mmer` For better results with the above method, :e frequency vibrational energy is intercepted and ex- :ted from the water at a point that is spaced from the mmer's breathing air valves and from the swimmers ving limbs whereby, of the noise generated by the athing supply and by the strokes of the swimmers is and the kicks of his feet the percentage that is rcepted, extracted from the water, and amplified is limized. Satisfactory results have been obtained by rceptng and extracting vibrational voice frequency rgy from the water adjacent the pelvic region of the mmer.

)ne apparatus, not shown, for carrying out the method udes hollow ear plugs which connect to thin walled ipliant hollow rubber balls or to a short broad horn two horns respectively for directional response) whose is covered by a thin compliant membrane of low ness and inertia and which has many times the area the ear drum. For purposes of pressure equalizathe ear drum side of the thin compliant member is pled to the breathing air supply. lnother apparatus for carrying out the method inles a small underwater transducer 10 sensitive to vi- ;ional voice frequency energy. Some transducers sen- 'e to the voice frequency range are too cumbersome this purpose. A crystal contact microphone of the used on stringed instruments is one example of an troacoustic transducer that is suiciently sensitive and ll enough to -be supported comfortably adjacent the nmers pelvic region. It is supported with its sensisurface in contact with the water. A crystal contact rophone made by Brush and marketed commery as VM-l crystalVibromike, covered with a rubboot, and whose dimensions are 1A inch thick, 3A wide and 2 inch long is suitable. The transducer is ed in latex (e.g., GACO N700) to protect "it from osion. An audio frequency amplifier 12 designed compactness (utilizing miniature tubes or transistors, ted circuitry, small batteries) is connected to trans- :r 10 and is supported on a belt around the swimmers 1t. A bone conduction electroacoustic transducer 14 onnected to the output of the amplifier and is suped on the swimmers head; it may be the bone conductype used with hearing aids. Where a bone conducheadset is worn over the ears, the swimmers ears t be ooded or pressure on his ear drums must otherbe equalized as by connecting an air tubing between breathing apparatus and the ears. The mask over swimmers mouth is functionally related to the reider of the apparatus through the medium of the amer. oise generated in the swimmers body by blood circun and other internal processes is negligible and does interfere with voice communication. )me binaural discrimination may be realized with invention by using two transducers 10, two amplifiers and two transducers 14, and by covering at least the 'e head, with a pressure release material to restrict ption of noise energy from the water by bone conion in the skull. Binaural discrimination is limited he fact that sound travels about 4.5 times faster in r than in air. The spacing between the two transrs 10 would have to be considerably greater than spacing between the ears to realize significant binl discrimination. The latter arrangement tends :nder the apparatus cumbersome. nviously many modifications and variations of the :nt invention are possible in the light of the above 4 teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.

We claim:

1. An improved method by which a plurality of underwater swimmers may continuously confer with one another while submerged in water comprising, at each swimmer, continuously intercepting and extracting from the water immediately adjacent the swimmer a fraction of any acoustic energy in the voice frequency range, amplifying the energy intercepted and extracted from the water adjacent the swimmer, continuously transferring the amplified voice frequency acoustic energy to the auditory nerve of the swimmer, continuously providing an air space around the nose and mouth of the swimmerY for breathing purposes and to continuously enable the swimmer to speak into the air space concurrently while listening to voice frequency energy transferred to his auditory nerve.

2. An improved method by which a plurality of underwater swimmers may continuously confer with one another while submerged in water comprising, at each swimmer, continuously intercepting, extracting from the water, and amplifying a fraction of any voice frequency acoustic energy present in the water adjacent only the pelvic region of the swimmer so that the amplified voice frequently acoustic energy includes a minimum percentage of acoustic energy arising from limb movement and breathing of the swimmer, continuously transferring the amplified voice frequency vibrational energy to the auditory nerve of the swimmer, continuously blocking the water from the nasal passages of 4the swimmer, continuously providing an air space around the mouth of the swimmer to continuously enable the swimmer to speak into the air space concurrently with listening to voice frequency energy transferred to his auditory nerve, and coupling the acoustic energy of speech from the air space, head, neck and chest of the swimmer into the water for transfer to the other swimmers.

3. An improved method by which a plurality of underwater swimmers may continuously confer with one another while submerged i`n water comprising, at each swimmer, continuously intercepting and extracting from the water immediately adjacent the swimmer a fraction of any voice frequency acoustic energy present in the water adjacent the swimmer, continuously amplifying said voice frequency acoustic energy, continuously transferring the amplified voice frequency acoustic energy to the auditory nerve of the swimmer, continuously blocking the water from the nasal passages of the swimmer, continuously providing an air space around the mouth of the swimmer to continuously enable the swimmer to speak into the air space concurrently while listening to voice frequency energy transferred to his auditory nerve, supplying air for breathing to the swimmer, and transferring acoustic energy of speech generated by the swimmer from the air space around the mouth, from the head surface, neck surface and upper trunk surface of the swimmer to the water for transfer to the other swimmers.

' 4. Equipment ior use by underwater swimmers in continuous conference voice communication with one another while swimming submerged, which comprises, for each swimmer, an underwater electromechanical transducer for voice frequencies, means mounting said transducer for support on the lower portion of the trunk of a swimmers body, voice frequency sensitive means mounted for attachment to the swimmers body, electrically connected directly to said transducer and continuously amplifying voice frequency electric currents from said transducer that are created by vibrations applied to said transducer from water in which the transducer is immersed, a head set electrically connected directly to said voice frequency means and transducing said amplified voice frequency currents into voice frequency vibrations applied to the head of the swimmer, and a mask to be worn by the swimmer over his month and nose by which the` swimmer may talk into the mask and through which a stream of air for breathing may be supplied, and create sound vibrations transmitted from the mask and the swimmers body into the water in which the swimmer is immersed for transmission through the water to another swimmer, and the transducer will receive a minimum of mechanical vibrations due to movements of the swimmers limbs in the water and the vibrations from the breathing air supply to the mask.

5. Equipment by which a plurality of persons while submerged n water may continuously confer with one another as they can in an air-filled room, which comprises, for each individual person, means for submergence in the water for receiving and amplifying voice frequency acoustic energy in the water adjacent thereto and without changing the frequency character of said energy, means supporting such means for attachment to such individual person, means for applying said amplified energy from said receiving7 means to the auditory nerve of that individual person, a face mask formed to fit such individual persons mouth to enable breathing when air is supplied thereto and for providing an air space in front of the mouth into which such individual person may speak at any time, and which mask can transfer some of the acoustic energy of speech in the air space into the surrounding water for transmission to another submergc person.

References Cited in the file of this patent (Ships), 16 Feb. 1956 (pp. 1-18). r-

Comparison of Hearing Thresholds in Air and i Water, by Wainwright, Journal of they Acoustical Sc 25 ciety of America, vol. 30, No. 11, Nov. 1958 (pp. 1025 1029 relied on). 

1. AN IMPROVED METHOD BY WHICH A PLURALITY OF UNDERWATER SWIMMERS MAY CONTINUOUSLY CONFER WITH ONE ANOTHER WHILE SUBMERGED IN WATER COMPRISING, AT EACH SWIMMER, CONTINUOUSLY INTERCEPTING AND EXTRACTING FROM THE WATER IMMEDIATELY ADJACENT THE SWIMMER A FRACTION OF ANY ACOUSTIC ENERGY IN THE VOICE FREQUENCY RANGE, AMPLIFYING THE ENERGY INTERCEPTED AND EXTRACTED FROM THE WATER ADJACENT THE SWIMMER, CONTINUOUSLY TRANSFERRING THE AMPLIFIED VOICE FREQUENCY ACOUSTIC ENERGY TO THE AUDITORY NERVE OF THE SWIMMER, CONTINUOUSLY PROVIDING AN AIR SPACE AROUND THE NOSE AND MOUTH OF THE SWIMMER FOR BREATHING PURPOSES AND TO CONTINUOUSLY ENABLE THE SWIMMER TO SPEAK INTO THE AIR SPACE CONCURRENTLY WHILE LISTENING TO VOICE FREQUENCY ENERGY TRANSFERRED TO HIS AUDITORY NERVE. 